Dry apply adhesive graphic films

ABSTRACT

An adhesive composition includes a blend of a pressure sensitive adhesive and an additive. The pressure sensitive adhesive includes a (meth)acrylate polymer. The additive includes a copolymer with a vinyl polymeric backbone that includes at least one free radically polymerizable vinyl monomer A and at least one reinforcing comonomer B, wherein B is present at 0 to about 20% by weight of the copolymer, and a pendant polysiloxane monomer grafted to the backbone. The adhesive composition may optionally be crosslinked. The adhesive composition may be applied to a film to form a graphic article. These graphic articles may be applied to a substrate without liquid application aids.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 11/374,236, filed Mar.13, 2006, now allowed, the disclosure of which is incorporated byreference in its entirety herein.

BACKGROUND

This disclosure relates to adhesive-backed graphic articles. Moreparticularly, this disclosure relates to large format adhesive-backedgraphic articles that may be used, for example, to make backlit signs.

Large-format graphic articles, which typically include a thin polymericfilm backed by a pressure sensitive adhesive, may be difficult to handleand apply onto a surface of a substrate. During the application processthe thin polymeric film may fold and stick onto itself, or the adhesivemay prematurely adhere to the surface of the substrate.

The adhesive-backed graphic articles may be applied onto a surface of aplastic sign substrate to make a backlit sign. The graphic article maybe applied onto the surface of the plastic sign substrate by spraying aliquid, typically a water/surfactant solution, onto the adhesive side ofthe graphic, and optionally onto the substrate surface. The liquidtemporarily “detackifies” the pressure sensitive adhesive so theinstaller may handle, slide, and re-position the graphic article into adesired position on the substrate surface. The liquid also allows theinstaller to pull the graphic article apart if it sticks to itself orprematurely adheres to the surface of the substrate. Applying a liquidto the adhesive may also improve the appearance of the installed graphicby providing a smooth, bubble free appearance with good adhesion buildon the surface of the substrate.

SUMMARY

While applying a liquid and/or a surfactant solution to the adhesive ona graphic article may in some respects provide a more convenientinstallation, the liquid also makes installing a graphic article arather messy process. In addition, if the graphic article is applied to,for example, a plastic substrate to make a sign, the substrate retainsmoisture after the installation process is complete. This retainedmoisture requires air drying for an extended period, typically at leastone day, before the sign may be rolled up, thermoformed, or otherwiseused. The retained moisture may also increase outgassing from somepolymeric materials commonly used in backlit signage applications suchas, for example, polycarbonates. This outgassing may cause formation ofbubbles beneath the graphic article, which makes the sign lessattractive to the viewer.

In one embodiment, this disclosure is directed to an adhesivecomposition including a blend of a pressure sensitive adhesive and anadditive. The pressure sensitive adhesive includes a (meth)acrylatepolymer. The additive includes a copolymer with a vinyl polymericbackbone that includes at least one free radically polymerizable vinylmonomer A and at least one reinforcing comonomer B, wherein B is presentat 0 to about 20% by weight of the copolymer, and a pendant polysiloxanemonomer grafted to the backbone. The polysiloxane monomer is present at0.01 to 50% by weight of the copolymer and has a number averagemolecular weight of 500 to 50,000. The blend includes less than 1% byweight of the polysiloxane monomer.

In another embodiment, this disclosure is directed to an adhesivecomposition including a blend of a pressure sensitive adhesive, anadditive and a crosslinker. The pressure sensitive adhesive includes a(meth)acrylate polymer. The additive includes a copolymer with a vinylpolymeric backbone including at least one free radically polymerizablevinyl monomer A and at least one reinforcing comonomer B, wherein B ispresent at 0 to about 20% by weight of the copolymer, and a pendantpolysiloxane monomer grafted to the backbone. The polysiloxane monomeris present at 0.01 to 50% by weight of the copolymer, and has a numberaverage molecular weight of 500 to 50,000.

In another embodiment, this disclosure is directed to an articleincluding a polymeric film having thereon a layer of an adhesivecomposition. The adhesive composition includes a blend of an adhesiveand an additive. The adhesive includes a (meth)acrylate polymer. Theadditive includes a copolymer with a vinyl polymeric backbone having aat least one free radically polymerizable vinyl monomer A and at leastone reinforcing comonomer B, wherein B is present at up to about 20% byweight of the copolymer, and a pendant polysiloxane monomer grafted tothe backbone. The polysiloxane monomer is present at 0.01 to 50% byweight of the copolymer has a number average molecular weight of 500 to50,000.

In another embodiment, this disclosure is directed to a graphic articleincluding an imageable polymeric film and a layer of adhesive on thefilm. The layer of adhesive includes a blend of a pressure sensitiveadhesive and up to 50% by weight of an additive. The pressure sensitiveadhesive includes a (meth)acrylate polymer. The additive includes apolysiloxane monomer with a number average molecular weight of 500 to50,000. A release liner is on the layer of adhesive, and the releaseliner has a microstructured surface adjacent to the layer of adhesive.

In yet another embodiment, this disclosure is directed to a method ofapplying a graphic article to a substrate. The method includes providinga graphic article that includes an imageable polymeric film and a layerof an adhesive on the film. The adhesive includes a blend of a pressuresensitive adhesive and an additive. The pressure sensitive adhesiveincludes a (meth)acrylate polymer, and the additive includes apolysiloxane monomer. A release liner resides on the layer of adhesive,wherein the release liner has a microstructured surface adjacent to thelayer of adhesive. At least a portion of the release liner is removed,and a surface of the layer of adhesive is adhered to a surface of asubstrate. The surface of the adhesive layer and the surface of thesubstrate are dry.

In another embodiment, this disclosure is directed to a sign including atransparent or translucent substrate, an adhesive layer on thesubstrate, and an imageable polymeric film on the adhesive layer. Theadhesive layer includes a blend of a pressure sensitive adhesive and anadditive. The pressure sensitive adhesive includes a (meth)acrylatepolymer, and the additive includes a polysiloxane monomer. The adhesivelayer has a microstructured surface.

It is not necessary for an installer to wet these graphic articles priorto applying them on a surface of a substrate. During a dry installationprocess, the graphic articles described in this disclosure may be pulledapart if the film unexpectedly folds and sticks to itself. Even ifinstalled dry, the graphic articles described herein may slide over thesubstrate surface and easily be moved into a precise position on thesurface. The level of adhesion between the graphic article and thesubstrate builds more quickly than in wet applications, and the adheredgraphic article may be rolled up, thermoformed, or used in any othermanner without drying. The dry installation minimizes outgassing fromplastics, which provides a graphic with a smooth, uniform, substantiallybubble-free appearance.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The Figures, Detailed Description and Examples which followmore particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a microstructured adhesiveon an graphic article;

FIG. 2 is a schematic cross-sectional view of the microstructuredadhesive on the graphic article of FIG. 1 as it is contacted with asubstrate; and

FIG. 3 is a schematic cross-sectional view of the microstructuredadhesive on the graphic article of FIG. 1 after dry lamination to thesubstrate.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention. The Figure elements are not drawnto any particular scale and individual elements' sizes are presented forease of illustration.

DETAILED DESCRIPTION

In one aspect, the present disclosure is directed to an adhesivecomposition that may be used, for example, to adhere a graphic articleto a surface of a substrate to form a backlit sign. The materials in theadhesive composition are selected such that the adhesive does not stickwell to itself under application conditions. Therefore, if the graphicarticle is unexpectedly folded onto itself during installation, it maybe easily pulled apart. The materials for the adhesive composition arealso selected such that, during the application process, the graphicarticle may be temporarily removable from and repositionable on thesubstrate after the graphic article is applied. Materials for theadhesive composition are also selected to provide initial adhesion,wetout rate, extent of wetout and final adhesion such that the graphicarticle adheres well to the substrate over time and forms a sufficientlystrong bond.

The adhesive composition is a blend of an adhesive including a(meth)acrylate polymer, and an additive including a copolymer with avinyl polymeric backbone and a pendant polysiloxane monomer attached tothe backbone.

The adhesive in the blend is preferably a pressure sensitive adhesive(PSA). Suitable PSAs possess properties including (1) aggressive andpermanent tack, (2) adherence with no more than finger pressure, (3)sufficient ability to hold onto an adherend, and (4) sufficient cohesivestrength. Materials that have been found to function well as PSAsinclude polymers designed and formulated to exhibit the requisiteviscoelastic properties resulting in a desired balance of tack, peeladhesion, and shear holding power.

The adhesive in the adhesive composition may be selected from any(meth)acrylate copolymer having the desired properties of a PSA. The(meth)acrylate copolymer is generally prepared by polymerizing(meth)acrylate monomers. Acrylate and methacrylate monomers are referredto collectively herein as “(meth)acrylate” monomers. Polymers preparedfrom one or more of such (meth)acrylate monomers, optionally with anyone or more of a variety of other useful monomers, will be referred tocollectively as “polyacrylates.” The polymers can be homopolymers orcopolymers, optionally in combination with other, non-(meth)acrylate,e.g., vinyl-unsaturated, monomers. Such polyacrylate polymers and theirmonomers are well-known in the polymer and adhesive arts, as are methodsof preparing the monomers and polymers.

Such poly(meth)acrylate polymers are formed, for example, bypolymerizing one or more monomeric acrylic or methacrylic esters ofnon-tertiary alkyl alcohols, with the alkyl groups having from 1 toabout 20 carbon atoms (e.g., from 3 to 18 carbon atoms). Suitableacrylate monomers include, for example, methyl acrylate, ethyl acrylate,n-butyl acrylate, 2-methylbutyl acrylate (2-MBA), lauryl acrylate,2-ethylhexyl acrylate, cyclohexyl acrylate, iso-octyl acrylate,octadecyl acrylate, nonyl acrylate, decyl acrylate, and dodecylacrylate. The corresponding methacrylates are useful as well. Alsouseful are aromatic acrylates and methacrylates, e.g., benzyl acrylate.Optionally, one or more monoethylenically unsaturated co-monomers may bepolymerized with the acrylate or methacrylate monomers. The particulartype and amount of co-monomer is selected based upon the desiredproperties of the polymer.

One group of useful co-monomers includes those having a homopolymerglass transition temperature greater than the glass transitiontemperature of the (meth)acrylate homopolymer. Examples of suitableco-monomers falling within this group include acrylic acid, acrylamides,methacrylamides, substituted acrylamides (such as N,N-dimethylacrylamide), itaconic acid, methacrylic acid, acrylonitrile,methacrylonitrile, vinyl acetate, N-vinyl pyrrolidone, isobornylacrylate, cyano ethyl acrylate, N-vinylcaprolactam, maleic anhydride,hydroxyalkyl(meth)acrylates, N,N-dimethylaminoethyl (meth)acrylate,N,N-diethylacrylamide, beta-carboxyethyl acrylate, vinyl esters of acarboxylic acid (e.g., carboxylic acids such as neodecanoic,neononanoic, neopentanoic, 2-ethylhexanoic, propionic acids, or thelike), vinylidene chloride, styrene, vinyl toluene, and alkyl vinylethers.

A preferred adhesive in the blend includes copolymers with 98 to 90parts by weight of 2-MBA and 2 to 10 parts by weight of acrylic acid.Another preferred adhesive in the blend includes copolymers with 98 to90 parts by weight of isooctyl acrylate and 2 to 10 parts by weight ofacrylic acid. Yet another preferred adhesive in the blend includescopolymers with 98 to 90 parts by weight of isooctyl acrylate and 2 to10 parts by weight of acrylamide. Even another preferred adhesive in theblend include copolymers with 98 to 90 parts by weight of 2-MBA and 2 to10 parts by weight of acrylamide.

While not wishing to be bound by any theory, it is believed that theadditive in the adhesive composition includes siloxane moieties that canconcentrate at a low energy surface thereof and form a siloxane-richsurface region. Once the adhesive composition is applied to a surface ofa substrate, the siloxane moieties can migrate away from thesiloxane-rich surface region and allow adhesion between the adhesivecomposition and substrate to build as the graphic article contacts thesurface of the substrate over time.

The additive includes a copolymer with a vinyl polymeric backbone and apendant polysiloxane monomer attached to the backbone. Suitablecopolymer additive compositions are described in U.S. Pat. No.4,693,935, which is incorporated by reference herein. This referencedescribes a composition including a copolymer having a vinyl polymericbackbone having grafted thereto pendent polysiloxane moieties. Anexposed surface of these compositions is initially repositionable on asubstrate to which it will be adhered but, once adhered, builds adhesionto form a strong bond.

The surface characteristics of the adhesive composition can bechemically tailored through variation of both the molecular weight ofthe grafted siloxane polymeric moiety and the total siloxane content(weight percentage) of the copolymer additive, with higher siloxanecontent and/or molecular weight providing lower initial adhesion, i.e.,a greater degree of repositionability. The chemical nature and themolecular weight of the vinyl polymeric backbone of the copolymer canalso be chosen such that the rate of adhesion build and the ultimatelevel of adhesion to the substrate can be matched to the requirements ofa particular application. Longer-term repositionability may thus beachieved if so desired.

The siloxane polymeric moieties in the additive can be grafted bypolymerizing a monomer onto reactive sites located on the backbone, byattaching preformed polymeric moieties to sites on the backbone, or bycopolymerizing the vinyl monomer(s), A, and, when used, reinforcingmonomer(s), B, with preformed polymeric siloxane monomer, C. Since thepolymeric siloxane surface modifier is chemically bound, it is possibleto chemically tailor the PSA compositions of this invention such that aspecific degree of repositionability is provided and can be reproducedwith consistency. The initial adhesion properties of even highlyaggressive PSA coatings can be varied over a broad range of values in acontrolled fashion, and the need for an additional process step.

The A monomer or monomers (there may be more than one) can be chosensuch that a tacky or tackifiable material is obtained uponpolymerization of A (or A and B). Representative examples of A monomersare the acrylic or methacrylic acid esters of non-tertiary alcohols suchas methanol, ethanol, 1-propanol, 2-propanol, 1-butanol,2-methyl-1-propanol, 1-pentanol, 2-pentanol, 3-pentanol,2-methyl-1-butanol, 1-methyl-1-butanol, 3-methyl-1-butanol,1-methyl-1-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol,cyclohexanol, 2-ethyl-1-butanol, 3-heptanol, benzyl alcohol, 2-octanol,6-methyl-1-heptanol, 2-ethyl-1-hexanol, 3,5-dimethyl-1-hexanol,3,5,5-trimethyl-1-hexanol, 1-decanol, 1-dodecanol, 1-hexadecanol,1-octadecanol, and the like, the alcohols having from 1 to 18 carbonatoms with the average number of carbon atoms being about 4-12, as wellas styrene, vinyl esters, vinyl chloride, vinylidene chloride, and thelike. Such monomers are known in the art, and many are commerciallyavailable. In some embodiments, polymerized A monomer backbonecompositions include poly(isooctyl acrylate), poly(isononyl acrylate),poly(isodecyl acrylate), poly(2-ethylhexyl acrylate), and copolymers ofisooctyl acrylate, isononyl acrylate, isodecyl acrylate, or 2-ethylhexylacrylate with other A monomer or monomers. Preferred polymerized Amonomer backbone compositions include poly(isooctyl acrylate).

Representative examples of reinforcing monomer, B, are polar monomerssuch as acrylic acid, methacrylic acid, itaconic acid, acrylamide,methacrylamide, N,N-dimethylacrylamide, acrylonitrile,methacrylonitrile, and N-vinyl pyrrolidone. In addition, polymericmonomers or macromonomers (as will be described hereinafter) having aT_(g) or T_(m) above 20° C. are also useful as reinforcing monomers.Representative examples of such polymeric monomers are poly(styrene),poly(alpha-methylstyrene), poly(vinyl toluene), and poly(methylmethacrylate) macromonomers. In some embodiments, B monomers are acrylicacid, acrylamide, methacrylic acid, N-vinyl pyrrolidone, acrylonitrile,and poly(styrene) macromonomer. In illustrative embodiments, the amountby weight of B monomer does not exceed 20% of the total weight of allmonomers such that excessive firmness of the PSA is avoided. In someembodiments, incorporation of B monomer to the extent of 2% to 15% byweight can provide a PSA of high cohesive or internal strength whichalso retains good adhesive properties. Preferred B monomers includemethacrylic acid and acrylic acid.

The C monomer can have the general formula:

X(Y)_(n)Si(R)_(3-(m+n))Z_(m)

where X is a vinyl group copolymerizable with the A and B monomers, Y isa divalent linking group, n is zero or 1, m is an integer of from 1 to 3such that m+n is not greater than 3; R is hydrogen, lower alkyl (e.g.,methyl, ethyl, or propyl), aryl (e.g., phenyl or substituted phenyl), oralkoxy, and Z is a monovalent siloxane polymeric moiety having a numberaverage molecular weight above about 500 and is essentially unreactiveunder copolymerization conditions.

The monomers are copolymerized to form the polymeric backbone with the Cmonomer grafted thereto and wherein the amount and composition of Cmonomer in the copolymer is such as to provide the PSA composition witha decrease (preferably of at least 20%) in the initial peel adhesionvalue relative to that of a control composition wherein the polysiloxanegrafts are absent.

Copolymers containing C monomer having a molecular weight less thanabout 500 may be less effective in providing repositionability.Copolymers containing C monomer having a molecular weight greater than50,000 effectively provide repositionability, but, at such highmolecular weights, possible incompatibility of the C monomer with theremaining monomer during the copolymerization process may result inreduced incorporation of C. C monomer molecular weight can range fromabout 500 to about 50,000. In some embodiments, a molecular weight canrange from about 5,000 to about 25,000.

In some embodiments, the C monomer is incorporated in the copolymer inthe amount of 0.01 to 50% of the total monomer weight to obtain thedesired degree of repositionability. The amount of C monomer includedmay vary depending upon the particular application, but incorporation ofsuch percentages of C monomer having a molecular weight in theabove-specified range has been found to proceed smoothly and to resultin material which provides effective repositionability for a variety ofapplications while still being cost effective. In general, it isdesirable to have a decrease (preferably of at least 20%) in the initialpeel adhesion value relative to that of a control containing nosiloxane. It is of course possible, however, that a person skilled inthe art might wish, for a specific purpose, to decrease the percentreduction in the initial peel as compared to the control.

In some embodiments, the total weight of B and C monomers is within therange of 0.01 to 70% of the total weight of all monomers in thecopolymer.

In some embodiments, the C monomer and certain of the reinforcingmonomers, B, are terminally functional polymers having a singlefunctional group (the vinyl group) and are sometimes termedmacromonomers or “macromers”. Such monomers are known and may beprepared by the method disclosed by Milkovich et al., as described inU.S. Pat. Nos. 3,786,116 and 3,842,059. The preparation ofpolydimethylsiloxane macromonomer and subsequent copolymerization withvinyl monomer have been described in several papers by Y. Yamashita etal., [Polymer J. 14, 913 (1982); ACS Polymer Preprints 25 (1), 245(1984); Makromol. Chem. 185, 9 (1984)]. This method of macromonomerpreparation involves the anionic polymerization ofhexamethylcyclotrisiloxane monomer to form living polymer of controlledmolecular weight, and termination is achieved via chlorosilane compoundscontaining a polymerizable vinyl group. Free radical copolymerization ofthe monofunctional siloxane macromonomer with vinyl monomer or monomersprovides siloxane-grafted copolymer of well-defined structure, i.e.,controlled length and number of grafted siloxane branches.

Preferred additives in the blend include copolymers with any of 93 to 78parts by weight of 2-MBA, isooctyl acrylate, or 2-ethylhexyl acrylate, 2to 10 parts by weight of acrylic acid or acrylamide, and 5-20 parts byweight of the polysiloxane monomer. Particularly preferred additives inthe blend include copolymers with 83 parts by weight of isooctylacrylate, 7 parts by weight of acrylic acid and 10 parts by weight ofthe polysiloxane monomer.

The amount of polysiloxane monomer in the adhesive composition may becontrolled by varying the amount of the polysiloxane monomer in theadditive, or by varying the amount of the additive in the blend. Theadhesive composition includes less than 1% by weight, or less than 0.9%by weight, or less than 0.5% by weight, or 0.1% by weight of thepolysiloxane monomer. The additive is typically present in the blend atgreater than 0% and up to 50% by weight, or greater than 0% by weightand up to 30% by weight, or greater than 0% and up to 10% by weight, orgreater than 0% by weight and up to 5% by weight.

The adhesive composition may optionally be crosslinked using methodsknown in the art, and the crosslinker and/or crosslinking technique maybe selected depending on the adhesives and additives used. The degree ofcrosslinking may be selected based upon the application for which thearticle is intended. The adhesive composition may be crosslinked by anyconventional technique including, for example, covalent, ionic orphysical crosslinking. For example, covalent crosslinks may be formed bythe use of ionizing radiation such as e-beam; by the use of ultravioletradiation in the presence of a photoactive functional group such asbenzophenone; or, by traditional reactive chemical means such as thereaction of a carboxylic acid group with an aziridine group. Ioniccrosslinks may be formed by interaction of an acidic group and a basicgroup. Examples of physical crosslinks include high Tg polymer segmentsincluded, for example, thermoplastic elastomeric block copolymers. Suchsegments aggregrate to form physical crosslinks that dissipate uponheating.

The adhesive composition may optionally include one or more additivessuch as initiators, fillers, plasticizers, tackifiers, chain transferagents, fibrous reinforcing agents, foaming agents, antioxidants,stabilizers, fire retardants, viscosity modifying agents, coloringagents, and mixtures thereof.

The adhesive composition may be applied to major surface of a polymericfilm to form a graphic article. The polymeric film used in the graphicarticle may vary widely depending on the intended application. Suitablefilms include polyesters, polyolefins polyacrylates, polyurethanes andvinyls. Typically, the films include plasticized polyvinyl chloride(PVC) with a thickness of about 2-4 mils (0.005 cm to 0.010 cm).Suitable films may have an imageable surface opposite the surface onwhich the adhesive is applied. The imageable surface may have an imageapplied by conventional printing techniques, including ink jet printing,screen printing, laser printing, electrostatic imaging, thermal masstransfer imaging and the like.

The adhesive composition may be applied to the polymeric film by anysuitable coating technique, and typically forms a smooth andsubstantially continuous layer having a thickness of about 15-50micrometers. The adhesive layer is typically covered by a release lineror transfer liner. The liner can be capable of being placed in intimatecontact with an adhesive and subsequently removed without damaging theadhesive layer. Non-limiting examples of liners include materials from3M of St. Paul, Minn., Loparex, Willowbrook Ill., P.S Substrates, Inc.,Schoeller Technical Papers, Inc., AssiDoman Inncoat GMBH, and P. W. A.Kunstoff GMBH. For example, the liner can be paper, a clay coated paper,a polymer-coated paper with a release coating, a polyethylene coatedpolyethylene terepthalate (PET) film with release coatings, or a castpolyolefin film with a release coating.

The surface of the adhesive opposite the film may be smooth or may havea structured topography. If the adhesive has a structured topography,the surface of the adhesive layer can have specific shapes that allowegress of air or other fluids trapped at the interface between theadhesive and a substrate as the graphic article is applied. Themicrostructures allow the adhesive layer to be uniformly adhered to orlaminated to a substrate without forming bubbles that could causeimperfections in the resulting laminate.

The microstructures on the adhesive layer (and correspondingmicrostructures on a release liner) can be microscopic in at least twodimensions. The term microscopic as used herein refers to dimensionsthat are difficult to resolve by the human eye without aid of amicroscope. One useful definition of microscopic is found in Smith,Modern Optic Engineering, (1966), pages 104-105, wherein visual acuityis defined and measured in terms of the angular size of the smallestcharacter that can be recognized. Normal visual acuity allows detectionof a character that subtends an angular height of 5 minutes of arc onthe retina.

The microstructures in the adhesive layer of the invention may be madeas described in U.S. Pat. Nos. 6,197,397 and 6,123,890, which are eachincorporated herein by reference. The topography may be created in theadhesive layer by any contacting technique, such as casting, coating orcompressing. The topography may be made by at least one of: (1) castingthe adhesive layer on a tool with an embossed pattern, (2) coating theadhesive layer onto a release liner with an embossed pattern, or (3)passing the adhesive layer through a nip roll to compress the adhesiveagainst a release liner with an embossed pattern. The topography of thetool used to create the embossed pattern may be made using any knowntechnique, such as, for example, chemical etching, mechanical etching,laser ablation, photolithography, stereolithography, micromachining,knurling, cutting or scoring.

A liner can be disposed on the microstructured adhesive layer and may beany release liner or transfer liner known to those skilled in the artthat in some cases are able of being embossed as described above. Theliner can be capable of being placed in intimate contact with anadhesive and subsequently removed without damaging the adhesive layer.Non-limiting examples of liners include materials from 3M of St. Paul,Minn., Loparex, Willowbrook Ill., P.S Substrates, Inc., SchoellerTechnical Papers, Inc., AssiDoman Inncoat GMBH, and P. W. A. KunstoffGMBH. The liner can be a polymer-coated paper with a release coating, apolyethylene coated polyethylene terepthalate (PET) film with releasecoatings, or a cast polyolefin film with a release coating.

The adhesive layer and/or release liner may optionally includeadditional non-tacky microstructures, including any of pegs, particlesand beads such as, for example, those described in U.S. Pat. Nos.5,296,277; 5,362,516; and 5,141,790. An example of such microstructuredadhesive layers with non-tacky microstructures includes those availablefrom 3M. St. Paul, Minn., under the trade designation Controltac Plus.

The microstructures may form a regular or a random array or pattern.Regular arrays or patterns include, for example, rectilinear patterns,polar patterns, cross-hatch patterns, cube-corner patterns. The patternsmay be aligned with the direction of the carrier web, or may be alignedat an angle with respect to the carrier web. The pattern ofmicrostructures may optionally reside on both major, opposing surfacesof the adhesive layer. This allows individual control of air egress andsurface area of contact for each of the two surfaces to tailor theproperties of the adhesive to two different interfaces.

The pattern of microstructures can define substantially continuous openpathways or grooves that extend into the adhesive layer from an exposedsurface. The pathways either terminate at a peripheral portion of theadhesive layer or communicate with other pathways that terminate at aperipheral portion of the article. When the article is applied to asubstrate, the pathways allow egress of fluids trapped at an interfacebetween the adhesive layer and a substrate.

The shapes of the microstructures in the adhesive layer may vary widelydepending on the level of fluid egress and peel adhesion required for aparticular application, as well as the surface properties of thesubstrate. Protrusions and depressions may be used, and in someembodiments the microstructures may be continuous grooves in theadhesive layer. Suitable shapes include hemispheres, V-grooves, andpyramids such as, for example, right pyramids, trigonal pyramids, squarepyramids, quadrangle pyramids, and truncated pyramids. The shapes may beselected for reasons such as, for example, pattern density, adhesiveperformance, and readily available methodology for producing themicrostructures. The microstructures may be systematically or randomlygenerated.

FIG. 1 is a schematic cross-sectional view of a microstructured adhesive120 on a film 110, which forms a graphic article 100. The graphicarticle 100 is preferably translucent, opaque or retroreflective. Atranslucent graphic article transmits visible light, may optionally becolored, and is not necessarily optically clear. An opaque graphicarticle substantially blocks visible light transmission. Aretroreflective graphic article reflects light preferentially backtoward its source, and suitable examples include those available from3M, St. Paul, Minn. under the trade designation SCOTCHLITE.

Referring again to FIG. 1, the embodiment shown has a plurality ofpyramidal protrusions 128 extending above a plane 123 of the adhesivelayer 120. The dimensions of the protrusions may vary widely dependingon the rheology of the adhesive layer and the application conditions,and should be selected to provide adequate balance between adhesion tosubstrate and fluid egress. In some embodiments, the mean pitch, p,between selected protrusions 128 is up to 400 micrometers, or 50 to 400micrometers, or from 100 to 350 micrometers, or from 180 to 300micrometers. In some embodiments, the mean height, h, of selectedprotrusions 128 from the plane 123 of the adhesive layer 120 can begreater than 1 micrometer and up to 35 micrometers, or 5 to 30micrometers, or 10 to 25 micrometers. Selected protrusions 128 have atleast one sidewall 132 that makes an angle a with respect to a plane 123of the surface of the adhesive layer 120. The angle a can be selectedfrom an angle greater than 5° and less than 40°, or from 5° to 15°, orfrom 5° to 10°. The gap between structures, g, is typically about 0% toabout 50% of the pitch p.

An optional release liner (not shown in FIG. 1) can be disposed on theadhesive layer 120. The release liner can have a topography thatcorresponds to the topography of the adhesive layer 120. In someembodiments, the release liner can provide a low surface energyinterface with the adhesive 120 which can allow siloxane moietiespresent in the adhesive 120 to concentrate at or near the surfaceinterface with the release liner.

Once the release liner is removed, the exposed surface of themicrostructured adhesive layer 120 may be contacted with a substrate 130to form a composite laminate 150, which may be a conventional graphic ora front lit or back lit sign. FIG. 2 is a schematic cross-sectional viewof the adhesive 120 and substrate 110 of FIG. 1 as it contacts asubstrate 130 to form a composite laminate 150.

The substrates 130 may be rigid or flexible. Examples of suitablesubstrates 130 include glass, metal, plastic, wood, and ceramicsubstrates, painted surfaces of these substrates, and the like.Representative plastic substrates include polyester, polyvinyl chloride,ethylene-propylene-diene monomer rubber, polyurethanes, polymethylmethacrylate, engineering thermoplastics (e.g., polyphenylene oxide,polyetheretherketone, polycarbonate), and thermoplastic elastomers. Forexample, to make a backlit sign, a suitable substrate is a flexibletranslucent plastic material available from 3M, St. Paul, Minn., underthe trade designation PANAFLEX. The substrate 130 may also be a wovenfabric formed from threads of synthetic or natural materials such as,for example, cotton, nylon, rayon, glass or ceramic material. Thesubstrate 130 may also be made of a nonwoven fabric such as air laidwebs of natural or synthetic fibers or blends thereof.

The process of applying the graphic article to a substrate is preferablysubstantially dry. For the purposes of this application, substantiallydry means that liquid application aids are not required to provideacceptable properties such as, for example, any or all of self-adhesion,initial adhesion to the substrate, slideability and repositionability onthe substrate, air/liquid egress, and final adhesion and wetoutproperties on the substrate.

As an example of this process, referring to FIG. 2, as the adhesivelayer 120 initially contacts a substrate 130, the pyramidal protrusions128 contact the surface of the substrate 130, and the areas 135 betweenthe protrusions 128 function as channels for fluid egress. This allowspockets of trapped air between the adhesive layer 120 and the substrate130 to be easily transported to an adhesive edge.

After removal of the protective release liner, the microstructures onthe surface of the adhesive layer retain their shape for a sufficienttime to maintain the fluid egress properties of the adhesive layer. Theselection of the adhesive also plays a role in determining the long-termproperties of the adhesive layer. After pressure is applied, themicrostructures on the adhesive layer may optionally collapse andincrease the amount of adhesive in contact with the substrate.

Referring to FIG. 3, in some embodiments, after adequate applicationconsistent with techniques known in the art, the channels 135 (shown inFIG. 2), if present, can at least partially disappear to provide thedesired adhesion to the substrates 130.

Advantages of the invention are illustrated by the following examples.However, the particular materials and amounts thereof recited in theseexamples, as well as other conditions and details, are to be interpretedto apply broadly in the art and should not be construed to unduly limitthe invention.

EXAMPLES

These examples are merely for illustrative purposes only and are notmeant to be limiting on the scope of the appended claims. All parts,percentages, ratios, etc. in the examples and the rest of thespecification are by weight, unless noted otherwise. Solvents and otherreagents used were obtained from Sigma-Aldrich Chemical Company;Milwaukee, Wis., unless otherwise noted.

Table of Abbreviations Abbreviation or Trade Designation DescriptionAdditive-1 A silicone modified polymer of 83 parts by weight ofiso-octyl acrylate, 7 parts by weight of acrylic acid, and 10 parts byweight of polysiloxane monomer as described in U.S. Pat. No. 4,693,935Example 36. This polymer was prepared and used as a 28.77% by weightsolution in ethyl acetate, isopropyl alcohol, and heptane. PSA-1 Acopolymer of 90 parts by weight of 2-methylbutyl acrylate and 10 partsby weight of acrylic acid. This polymer was prepared and used as a 40%by weight solution in heptane/acetone (65:35). Crosslinker-1 5% solidssolution in toluene of the crosslinker described in Example 1 of U.S.Pat. No. 5,296,277. Film-1 Nominally 50 micrometer thick plasticized,white flexible and conformable vinyl (PVC, polyvinyl chloride). Film-2Nominally 50 micrometer thick plasticized, yellow translucent andconformable vinyl (PVC, polyvinyl chloride). Acrylic Clear acrylicplastic sheet, about 3 millimeters thick available under Substrate thetrade name PLEXIGLAS. The sheet was washed with isopropyl alcohol andallowed to air dry. Liner-1 Flat clay-coated paper liner having a thinsilicone release layer. Liner-2 Polyolefin coated paper liner having athin silicone release layer and having a topography of side-adjacentsquare pyramidal recesses at a repeat pitch of about 200 micrometers,depth of about 15 micrometers, sidewall slopes of about 8 degrees fromhorizontal. Liner-3 Polyolefin coated paper liner having a thin siliconerelease layer and having a topography of recessed side-adjacent squarepyramidal features at a repeat pitch of about 292 micrometers, gapbetween recessed features of about 6 micrometers, depth of about 25micrometers, and sidewall slopes of about 10 degrees from horizontal.Liner-4 Polyolefin coated paper liner having a thin silicone releaselayer and having a topography of side-adjacent square pyramidal recessesat a repeat pitch of about 197 micrometers, depth of about 15micrometers, sidewall slopes of about 8 degrees from horizontal. Thetopography included a second pattern of a grid array at a repeat pitchof about 400 micrometers of small circular recessed pits The pits wereabout 50 micrometers in diameter, about 13 micrometers deep, and filledwith non-tacky ceramic beads. Laminate-1 Available from 3M Company, St.Paul, MN under the trade name 3630 Series SCOTCHCAL Marking Film.

Test Methods Self Adhesion Test

Liner was removed from the adhesive face of about a 15 centimeter long X10 centimeter wide film sample. The film sample was held adhesive faceup at the two lengthwise ends with two hands while the film was allowedto fold and hang loosely in between. The end edges were carefullybrought closer together to allow the two vertically hanging adhesivefaces of the film to gently contact each other, and then the two endswere pulled apart to separate the contacting adhesive faces. The extentof grab of the adhesive faces while separating them was recorded:difficult to separate—grab; very slight self adhesion and very easy toseparate—slight grab; essentially no self adhesion—no grab.

Slidability Test

Liner was removed from the adhesive face of about a 15 centimeter long X10 centimeter wide film sample, and at room temperature the adhesiveface of the sample was allowed to contact the smooth glass or AcrylicSubstrate panel under gravitational force. One lengthwise edge of thesample was held and pulled essentially horizontally to the panel. Theease of slidability was recorded: essentially no slide—slight; difficultto slide—limited; easily slides—OK; very easy to slide—excellent.

Air Bleed

Air bubble release was evaluated by applying the adhesive face of abouta 15 centimeter long X 10 centimeter wide film backing/PSA laminatesample onto a flat, smooth panel, applying finger pressure from edgestoward center to entrap some bubbles, and pressing at edges of bubblesto attempt to flatten graphic against panel. Results are listed as “Yes”or “No” if air bubbles are released or not.

Wetout Test

Using the pan of an electronic balance, the adhesive face of a filmsample was applied onto a panel of the Acrylic Substrate using fingerpressure to register about 500 g. on the balance. After about 5 minutesand after 24 hours at room temperature, the adhesive interface with theAcrylic Substrate was viewed through the panel from the opposite face ofthe panel using microscopy, and the percentage area of adhesive contactwas determined using image analysis.

180° Peel Adhesion

Samples were cut into 2.54 centimeter wide strips. The release liner wasremoved and the adhesive face of the film strip was adhered to the cleanAcrylic Substrate using a PA-1 plastic squeegee (available from 3M) andfirm application force. After the indicated dwell time, the sample wastested for 180° peel adhesion using an Instron Model 5564 universaltesting machine at a rate of 30 centimeters/minute (12 inches/minute).Five samples were tested for each condition, and the reported adhesionvalue is an average of the five samples.

Example 1

A mixture of the solutions of Additive-1, PSA-1, and Crosslinker-1 wasprepared to give 1 part by weight solids Additive-1, 99 parts by weightsolids PSA-1, and 0.15 parts by weight solids Crosslinker-1, coated ontoLiner-2 with a notch bar coater at a gap of about 125 micrometers, anddried in an oven at 70° C. for 10 minutes. Film-1 was laminated to thisconstruction. Liner-2 was removed and the adhesive coated film wastested for Self Adhesion Test, Slidability Test, Air Bleed Test, andWetout Test. The results are shown in Table 1.

Example 2

A mixture of the solutions of Additive-1, PSA-1, and Crosslinker-1 wasprepared to give 5 part by weight solids Additive-1, 95 parts by weightsolids PSA-1, and 0.13 parts by weight solids Crosslinker-1, coated ontoLiner-2 with a notch bar coater at a gap of about 76 micrometers, anddried in an oven at 70° C. for 10 minutes. Film 2 was laminated to thisconstruction. Liner-2 was removed and the adhesive coated film wastested for Self Adhesion Test, Slidability Test, Air Bleed Test, andWetout Test. The results are shown in Table 1.

Example 3

A mixture of the solutions of Additive-1, PSA-1, and Crosslinker-1 wasprepared to give 10 part by weight solids Additive-1, 90 parts by weightsolids PSA-1, and 0.15 parts by weight solids Crosslinker-1, coated ontoLiner-2 with a notch bar coater at a gap of about 125 micrometers, anddried in an oven at 70° C. for 10 minutes. Film-1 was laminated to thisconstruction. Liner-2 was removed and the adhesive coated film wastested for Self Adhesion

Test, Slidability Test, Air Bleed Test, and Wetout Test. The results areshown in Table 1.

Comparative Example C1

A mixture of the solutions of PSA-1 and Crosslinker-1 was prepared togive 100 parts by weight solids PSA-1 and 0.14 parts by weight solidsCrosslinker-1, coated onto Liner-1 with a notch bar coater at a gap ofabout 76 micrometers, and dried in an oven at 70° C. for 10 minutes.Film-2 was laminated to this construction. Liner-1 was removed and theadhesive coated film was tested for Self Adhesion Test, SlidabilityTest, Air Bleed Test, and Wetout Test. The results are shown in Table 1.

Comparative Example C2

Comparative Example C1 was repeated, but used Liner-2. Liner-2 wasremoved and the adhesive coated film was tested for Self Adhesion Test,Slidability Test, Air Bleed Test, and Wetout Test. The results are shownin Table 1.

Example 4

A mixture of the solutions of Additive-1, PSA-1, and Crosslinker-1 wasprepared to give 1 part by weight solids Additive-1, 99 parts by weightsolids PSA-1, and 0.15 parts by weight solids Crosslinker-1, coated ontoLiner-3 with a notch bar coater at a gap of about 125 micrometers, anddried in an oven at 70° C. for 10 minutes. Film-1 was laminated to thisconstruction. Liner-3 was removed and the adhesive coated film wastested for Self Adhesion Test, Slidability Test, Air Bleed Test, andWetout Test. The results are shown in Table 1.

Example 5

A mixture of the solutions of Additive-1, PSA-1, and Crosslinker-1 wasprepared to give 5 part by weight solids Additive-1, 95 parts by weightsolids PSA-1, and 0.15 parts by weight solids Crosslinker-1, coated ontoLiner-3 with a notch bar coater at a gap of about 125 micrometers, anddried in an oven at 70° C. for 10 minutes. Film-1 was laminated to thisconstruction. Liner-3 was removed and the adhesive coated film wastested for Self Adhesion Test, Slidability Test, Air Bleed Test, andWetout Test. The results are shown in Table 1.

Example 6

A mixture of the solutions of Additive-1, PSA-1, and Crosslinker-1 wasprepared to give 10 part by weight solids Additive-1, 90 parts by weightsolids PSA-1, and 0.15 parts by weight solids Crosslinker-1, coated ontoLiner-3 with a notch bar coater at a gap of about 125 micrometers, anddried in an oven at 70° C. for 10 minutes. Film-1 was laminated to thisconstruction. Liner-3 was removed and the adhesive coated film wastested for Self Adhesion Test, Slidability Test, Air Bleed Test, andWetout Test. The results are shown in Table 1.

Comparative Example C3

A mixture of the solutions of PSA-1 and Crosslinker-1 was prepared togive 100 parts by weight solids PSA-1 and 0.14 parts by weight solidsCrosslinker-1, coated onto Liner-3 with a notch bar coater at a gap ofabout 125 micrometers, and dried in an oven at 70° C. for 10 minutes.Film-1 was laminated to this construction. Liner-3 was removed and theadhesive coated film was tested for Self Adhesion Test, SlidabilityTest, Air Bleed Test, and Wetout Test. The results are shown in Table 1.

Example 7

A mixture of the solutions of Additive-1, PSA-1, and Crosslinker-1 wasprepared to give 5 part by weight solids Additive-1, 95 parts by weightsolids PSA-1, and 0.13 parts by weight solids Crosslinker-1, coated ontoLiner-4 with a notch bar coater at a gap of about 76 micrometers, anddried in an oven at 75° C. for 15 minutes. Film-2 was laminated to thisconstruction. Liner-4 was removed and the adhesive coated film wastested for Self Adhesion

Test, Slidability Test, Air Bleed Test, and Wetout Test. The results areshown in Table 1. A modified Wetout Test was performed using anapplication procedure that used a PA-1 plastic squeegee (available from3M) and firm application force, which gave an initial wetout of 80% anda 24 hour dwell wetout of 97%.

TABLE 1 Self Wet out Adhesion Slidability Air Bleed Wet out After 24Example Test Test Test Initial hours 1 Slight grab OK Yes NM NM 2 Slightgrab OK Yes 59 95 3 Slight grab OK Yes NM NM C1 Grab Slight No 78 99 C2Grab Limited Yes 59 95 4 Slight grab Excellent Yes NM 34 5 No grabExcellent Yes NM 31 6 No grab Excellent Yes NM 50 C3 grab Limited Yes NM34 7 No grab Excellent Yes 53-58 94 8 Slight grab Slight No NM NM NM =Not Measured

Example 8

A mixture of the solutions of Additive-1, PSA-1 and Crosslinker-1 wasprepared to give 5 parts by weight Additive-1, 95 parts by weight solidsPSA-1, and 0.14 parts by weight solids Crosslinker-1, coated intoLiner-1 with a notch bar coater at a gap of about 125 micrometers, anddried in an oven at 66° C. for 15 minutes. Film-2 was laminated to thisconstruction. Liner-1 was removed and the adhesive coated film wastested using the Self Adhesion Test, Slidability Test, and Air BleedTest. The results are shown in Table 1.

Example 9 and Comparative Example C4

For Example 9, samples of the adhesive/liner constructions prepared inExamples 2, 5, and 7 were laminated to an Acrylic Substrate and testedfor 180° Peel Adhesion according to the Test Method given above afterdwells of 0 hours (initial), 0.5, 1, 2, and 6 hours and after 5 days at23° C. and 50% relative humidity. All samples were applied dry usingfirm pressure from a PA-1 plastic squeegee. For Comparative Example C4,Laminate-1 was applied either using an aqueous detergent solution (asper product instructions) called wet lamination or dry as for Example 9.These data are shown in Table 2.

TABLE 2 180° 180° 180° 180° 180° 180° Peel Peel Peel Peel Peel PeelAdhesion Adhesion Adhesion Adhesion Adhesion Adhesion Example LaminationInitial 0.5 hour 1 hour 2 hours 6 hours 5 days Example Reference Method(N/dm) (N/dm) (N/dm) (N/dm) (N/dm) (N/dm) 9A 2 Dry 35 42 42 46 46 56 9B5 Dry 28 32 37 39 40 44 9C 7 Dry 33 35 33 37 42 67 C4A — Wet NM 1.1 1126 58 54 C4B — Dry 56 61 67 67 67 74 NM = Not Measured

The complete disclosure of all patents, patent documents, andpublications cited herein are incorporated be reference. The foregoingdetailed description and examples have been given for clarity ofunderstanding only. No unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, for variations obvious to one skilled in the art will beincluded within the invention defined by the claims.

1. An adhesive composition comprising a blend of: a pressure sensitiveadhesive comprising a (meth)acrylate polymer; and, an additivecomprising a copolymer, wherein the copolymer comprises: a vinylpolymeric backbone comprising a at least one free radicallypolymerizable vinyl monomer A and at least one reinforcing comonomer B,wherein B is present at 0 to about 20% by weight of the copolymer, and apendant polysiloxane monomer grafted to the backbone, wherein thepolysiloxane monomer is present at 0.01 to 50% by weight of thecopolymer, and wherein the polysiloxane monomer has a number averagemolecular weight of 500 to 50,000; and wherein the blend comprises lessthan 1% by weight of the polysiloxane monomer.
 2. The composition ofclaim 1, wherein the blend comprises less than or equal to 0.9% byweight of the polysiloxane monomer.
 3. The composition of claim 1,wherein the blend comprises less than or equal to 0.5% by weight of thepolysiloxane monomer.
 4. The composition of claim 1, wherein the blendcomprises less than or equal to 0.1% by weight of the polysiloxanemonomer.
 5. The composition of claim 1, wherein the pressure sensitiveadhesive is a copolymer comprising (meth)acrylate and (meth)acrylic acidmonomers.
 6. The composition of claim 5, wherein the (meth)acrylatemonomer is 2 MBA and the (meth)acrylic acid monomer is acrylic acid. 7.The composition of claim 6, wherein the pressure sensitive adhesivecomprises 90 parts by weight of 2 MBA and 10 parts by weight acrylicacid.
 8. The composition of claim 1, wherein A is selected from thegroup consisting of iso-octyl (meth)acrylate; ethyl (meth)acrylate,2-ethylhexyl (meth)acrylate and isodecyl (meth)acrylate, and B isselected from the group consisting of (meth)acrylic acid,n-vinyl-2-pyrrolidone, acrylamide, and polystyrene.
 9. The compositionof claim 8, wherein the copolymer comprises 83 parts by weight ofiso-octyl (meth)acrylate, 7 parts by weight of acrylic acid and 10 partsby weight of the polysiloxane monomer.
 10. The composition of claim 1,further comprising a crosslinker.
 11. An adhesive composition comprisinga blend of: a pressure sensitive adhesive comprising a (meth)acrylatepolymer; and, an additive comprising a copolymer, wherein the copolymercomprises: a vinyl polymeric backbone comprising a at least one freeradically polymerizable vinyl monomer A and at least one reinforcingcomonomer B, wherein B is present at 0 to about 20% by weight of thecopolymer, and a pendant polysiloxane monomer grafted to the backbone,wherein the polysiloxane monomer is present at 0.01 to 50% by weight ofthe copolymer, and wherein the polysiloxane monomer has a number averagemolecular weight of 500 to 50,000; and a crosslinker.
 12. Thecomposition of claim 11, wherein the pressure sensitive adhesive is acopolymer comprising (meth)acrylate and (meth)acrylic acid monomers. 13.The composition of claim 12, wherein the (meth)acrylate monomer is 2 MBAand the (meth)acrylic acid monomer is acrylic acid.
 14. The compositionof claim 11, wherein the pressure sensitive adhesive comprises 90 partsby weight of 2 MBA and 10 parts by weight acrylic acid.
 15. Thecomposition of claim 11, wherein A is selected from the group consistingof iso-octyl (meth)acrylate; ethyl (meth)acrylate, 2-ethylhexyl(meth)acrylate and isodecyl (meth)acrylate, and B is selected from thegroup consisting of (meth)acrylic acid, n-vinyl-2-pyrrolidone,acrylamide, and polystyrene.
 16. The composition of claim 11, whereinthe copolymer comprises 83 parts by weight of iso-octyl (meth)acrylate,7 parts by weight of acrylic acid and 10 parts by weight of thepolysiloxane monomer.
 17. The composition of claim 11, wherein thecrosslinker comprises less than 1% by weight of the composition.
 18. Thecomposition of claim 11, wherein the crosslinker comprises an aziridinecrosslinker.